From patchwork Sat Apr 6 17:36:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vincent Donnefort X-Patchwork-Id: 13619894 Received: from mail-yb1-f202.google.com (mail-yb1-f202.google.com [209.85.219.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1CB401D53F for ; Sat, 6 Apr 2024 17:37:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.219.202 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712425030; cv=none; b=DDKhwZNv5biA0L5O6rCpe7rDKbHGUIBkEbkqz0FLw5Vf4X+rBeYg96JblAQ149wnWXNHG/kXl2dh7RAgEMTCm/QvO73aIZu8Hh7Z31CzC8101lhfohI6rxpuEy+GbxqmHnlZ9ByeCD44+Q5mmOkRC8THoeNrsppF6+tGRwrUrNs= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1712425030; c=relaxed/simple; bh=x9DG/KzPXeuqYLfVwxHtnuzQ1Sd6OfT/JruaJGPsCpI=; h=Date:Mime-Version:Message-ID:Subject:From:To:Cc:Content-Type; b=pELFOTba6cHlJd0glvxzA6oAl/ByTioH6qgS43u7ceSxpHF4INpa3fL5Ge8GSkImzsTQtzeEaI+vSNkxBPtL+BMl81qPvAZ95IvLSZZK8jVGVeX1fHdvQNSbutvr7QGgoo7KODUHEYQVD6wEcgJ09JtOvWYaxpYDbDimtT1FMN4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=4yQk4rNC; arc=none smtp.client-ip=209.85.219.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--vdonnefort.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="4yQk4rNC" Received: by mail-yb1-f202.google.com with SMTP id 3f1490d57ef6-de0b4063e59so1798085276.3 for ; Sat, 06 Apr 2024 10:37:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1712425028; x=1713029828; darn=vger.kernel.org; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=WK1SjcPrgFwZI40moJ5xTOE82NN/79sUbus4GcyjLt0=; b=4yQk4rNCMWjAlxoP6oJhedLwn1CBicwB+0QSrBci8YDWPzoe1yXQy7SFlwQSU8vk9B aiaV6wmUXHlTeEGzcb+7GodfaGur+eLt/ly1fD6+AalJ/thM2L28Igm6wAcScdGts2R6 14kgHl8/JCOyJ+u+ysBlDOfwunMfs7LFDYSra/9nTjll0lLa6n+rCFlr5fLLbQ4ONB4D /afmrFOcAsy2mXRilAt1lfe4TK+UjowwBMbM7PD6BrP/VjkqBBtJ2WTVIDX3324g3ymj jjjAPVw3W+9RsIJ5Uu3NpMY/BCS+eRv3LeB85relyzZ9qHq+xXaDdhemNqZrhxBunR2e XTpQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1712425028; x=1713029828; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=WK1SjcPrgFwZI40moJ5xTOE82NN/79sUbus4GcyjLt0=; b=p/U6hRi+bwcTU+JG/xcBJ2c98cUdb+DWcMbT9323pvf/D/JrC4hMJbgRSGm/1Wd5Nv pYiJ/ClGs251rkY2rlIlU6yrFrj7PAjaK1LUn6fEVUZrdyMouwkOfTN+SnZ537hYYAVp 0am9L4bjJLrHUTE6SKRF6j/rYbsClgRbSva59f3gUxqxgeQ2Evt5tsKI03Ec2yZ3m6gw /mqRIdlhtRb/oyb77pY3uklRiywpJ+ntqtgE3HwCopFAlqyblx4RzUDC1FD+2AlJXxSy 159W5Zq5hotpqHFXElMXLXqcMTAna+/kMCjY/TtySuSeCnlcmphzNcE3n/Ysn9ISlNp/ FfiA== X-Forwarded-Encrypted: i=1; AJvYcCVmau93a33UCeCLNE4g7GH7zP5XwKNf7AiTe0Ex9qgMVII/Rti46H67RIV6mQ0NO1XzQ8wLLhejPRlnV57jUjLvJRyftRH405v+cgSsyD1055+w X-Gm-Message-State: AOJu0Yxx1i/5u+5Cu8C3AtJ+zDxLWpPVvpgCRKKsFmNDYt2XjowREiPA sIRxHhLhk1XfMeVHEOLmpcSa/3NpFEZqLsViWUt0IMpoo0t9CwUA0v6iZcdKizHljWTF2Te5yQA 9lXOgMtKwaBhAfjDmZw== X-Google-Smtp-Source: AGHT+IEjPcZE4m80n4E3CS1R5ulCRuvGZxKQvhtaMqaKgLVVomYXoaU5NC4fJo2eCbqjYxvUHtn1CdLZkfww/tWo X-Received: from vdonnefort.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:2eea]) (user=vdonnefort job=sendgmr) by 2002:a05:6902:100a:b0:dda:ce5f:b4c3 with SMTP id w10-20020a056902100a00b00ddace5fb4c3mr1453176ybt.1.1712425028177; Sat, 06 Apr 2024 10:37:08 -0700 (PDT) Date: Sat, 6 Apr 2024 18:36:44 +0100 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 X-Mailer: git-send-email 2.44.0.478.gd926399ef9-goog Message-ID: <20240406173649.3210836-1-vdonnefort@google.com> Subject: [PATCH v20 0/5] Introducing trace buffer mapping by user-space From: Vincent Donnefort To: rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: mathieu.desnoyers@efficios.com, kernel-team@android.com, rdunlap@infradead.org, Vincent Donnefort The tracing ring-buffers can be stored on disk or sent to network without any copy via splice. However the later doesn't allow real time processing of the traces. A solution is to give userspace direct access to the ring-buffer pages via a mapping. An application can now become a consumer of the ring-buffer, in a similar fashion to what trace_pipe offers. Support for this new feature can already be found in libtracefs from version 1.8, when built with EXTRA_CFLAGS=-DFORCE_MMAP_ENABLE. Vincent v19 -> v20: * Fix typos in documentation. * Remove useless mmap open and fault callbacks. * add mm.h include for vm_insert_pages v18 -> v19: * Use VM_PFNMAP and vm_insert_pages * Allocate ring-buffer subbufs with __GFP_COMP * Pad the meta-page with the zero-page to align on the subbuf_order * Extend the ring-buffer test with mmap() dedicated suite v17 -> v18: * Fix lockdep_assert_held * Fix spin_lock_init typo * Fix CONFIG_TRACER_MAX_TRACE typo v16 -> v17: * Documentation and comments improvements. * Create get/put_snapshot_map() for clearer code. * Replace kzalloc with kcalloc. * Fix -ENOMEM handling in rb_alloc_meta_page(). * Move flush(cpu_buffer->reader_page) behind the reader lock. * Move all inc/dec of cpu_buffer->mapped behind reader lock and buffer mutex. (removes READ_ONCE/WRITE_ONCE accesses). v15 -> v16: * Add comment for the dcache flush. * Remove now unnecessary WRITE_ONCE for the meta-page. v14 -> v15: * Add meta-page and reader-page flush. Intends to fix the mapping for VIVT and aliasing-VIPT data caches. * -EPERM on VM_EXEC. * Fix build warning !CONFIG_TRACER_MAX_TRACE. v13 -> v14: * All cpu_buffer->mapped readers use READ_ONCE (except for swap_cpu) * on unmap, sync meta-page teardown with the reader_lock instead of the synchronize_rcu. * Add a dedicated spinlock for trace_array ->snapshot and ->mapped. (intends to fix a lockdep issue) * Add kerneldoc for flags and Reserved fields. * Add kselftest for snapshot/map mutual exclusion. v12 -> v13: * Swap subbufs_{touched,lost} for Reserved fields. * Add a flag field in the meta-page. * Fix CONFIG_TRACER_MAX_TRACE. * Rebase on top of trace/urgent. * Add a comment for try_unregister_trigger() v11 -> v12: * Fix code sample mmap bug. * Add logging in sample code. * Reset tracer in selftest. * Add a refcount for the snapshot users. * Prevent mapping when there are snapshot users and vice versa. * Refine the meta-page. * Fix types in the meta-page. * Collect Reviewed-by. v10 -> v11: * Add Documentation and code sample. * Add a selftest. * Move all the update to the meta-page into a single rb_update_meta_page(). * rb_update_meta_page() is now called from ring_buffer_map_get_reader() to fix NOBLOCK callers. * kerneldoc for struct trace_meta_page. * Add a patch to zero all the ring-buffer allocations. v9 -> v10: * Refactor rb_update_meta_page() * In-loop declaration for foreach_subbuf_page() * Check for cpu_buffer->mapped overflow v8 -> v9: * Fix the unlock path in ring_buffer_map() * Fix cpu_buffer cast with rb_work_rq->is_cpu_buffer * Rebase on linux-trace/for-next (3cb3091138ca0921c4569bcf7ffa062519639b6a) v7 -> v8: * Drop the subbufs renaming into bpages * Use subbuf as a name when relevant v6 -> v7: * Rebase onto lore.kernel.org/lkml/20231215175502.106587604@goodmis.org/ * Support for subbufs * Rename subbufs into bpages v5 -> v6: * Rebase on next-20230802. * (unsigned long) -> (void *) cast for virt_to_page(). * Add a wait for the GET_READER_PAGE ioctl. * Move writer fields update (overrun/pages_lost/entries/pages_touched) in the irq_work. * Rearrange id in struct buffer_page. * Rearrange the meta-page. * ring_buffer_meta_page -> trace_buffer_meta_page. * Add meta_struct_len into the meta-page. v4 -> v5: * Trivial rebase onto 6.5-rc3 (previously 6.4-rc3) v3 -> v4: * Add to the meta-page: - pages_lost / pages_read (allow to compute how full is the ring-buffer) - read (allow to compute how many entries can be read) - A reader_page struct. * Rename ring_buffer_meta_header -> ring_buffer_meta * Rename ring_buffer_get_reader_page -> ring_buffer_map_get_reader_page * Properly consume events on ring_buffer_map_get_reader_page() with rb_advance_reader(). v2 -> v3: * Remove data page list (for non-consuming read) ** Implies removing order > 0 meta-page * Add a new meta page field ->read * Rename ring_buffer_meta_page_header into ring_buffer_meta_header v1 -> v2: * Hide data_pages from the userspace struct * Fix META_PAGE_MAX_PAGES * Support for order > 0 meta-page * Add missing page->mapping. Vincent Donnefort (5): ring-buffer: allocate sub-buffers with __GFP_COMP ring-buffer: Introducing ring-buffer mapping functions tracing: Allow user-space mapping of the ring-buffer Documentation: tracing: Add ring-buffer mapping ring-buffer/selftest: Add ring-buffer mapping test Documentation/trace/index.rst | 1 + Documentation/trace/ring-buffer-map.rst | 106 +++++ include/linux/ring_buffer.h | 6 + include/uapi/linux/trace_mmap.h | 48 +++ kernel/trace/ring_buffer.c | 403 +++++++++++++++++- kernel/trace/trace.c | 113 ++++- kernel/trace/trace.h | 1 + tools/testing/selftests/ring-buffer/Makefile | 8 + tools/testing/selftests/ring-buffer/config | 2 + .../testing/selftests/ring-buffer/map_test.c | 302 +++++++++++++ 10 files changed, 979 insertions(+), 11 deletions(-) create mode 100644 Documentation/trace/ring-buffer-map.rst create mode 100644 include/uapi/linux/trace_mmap.h create mode 100644 tools/testing/selftests/ring-buffer/Makefile create mode 100644 tools/testing/selftests/ring-buffer/config create mode 100644 tools/testing/selftests/ring-buffer/map_test.c base-commit: 7604256cecef34a82333d9f78262d3180f4eb525